The son of former Leinster and Wales coach Mike, Rhys Ruddock declared his allegiance to Ireland, the country of his birth, having represented Wales at Under-18 level. A member of the Leinster academy, he was selected for Ireland Under-20s as they contested the Junior World Championship in June 2010. During the tournament Ruddock was drafted into the full Ireland squad for the latter stages of their tour to Australia and New Zealand and played in defeats to the New Zealand Maori and Wallabies.